Multiple devices are known, in which a base station communicates with a remote unit. Some examples include baby monitor in which a stationery device is located adjacent to the baby, for example in or near his bed, and a mobile unit is carried by a parent or another caregiver; a cordless phone having a handset and a base station; a dog collar having thereon a mobile unit that communicates with another unit which may be stationary or mobile, or the like. Such devices operate using a variety of technologies, such as radio signals carrying digital or analog link, (RF), or the like.
Some of these devices are equipped with link-quality or range detector, i.e., a mechanism that constantly monitors the distance or communication quality between the remote unit and the other unit, which may be stationary or also mobile. The detector provides an alert to the person in charge should the distance exceed a threshold, or should signals emitted by one unit not be received with satisfactory quality by the other unit. The indication may be provided vocally, visually, or in any other manner.
In recent years there is greater awareness to possible risks of excess integrated radiation absorbed by users. In particular, parents as well as pet owners are reluctant to expose their babies, children or pets to unnecessary radiation. Therefore such devices had been designed which broadcast non-continuously from the baby or pet side, and establish communication with the other unit only when necessary, for example when the baby cries or makes other sounds. During quite periods, the unit placed near the baby is not broadcasting, thus reducing the amount of radiation the baby is exposed to.
However, some radiation is still emitted near the baby, as frequent communication is maintained between the units, in order to verify that the distance between the units remains acceptable and that the link is reliable. Such verification is necessary, since otherwise the caregiver may not receive the required communication even when the other side is broadcasting, for example when the baby cries.
There is thus a need for reduced-communication link quality or range monitoring or detection mechanism to be used in wireless systems in order to verify that the two units are at most a predetermined distance apart, or that data communicated between the units is of satisfactory quality.